@article{BUMI_1959_3_14_1_62_0, author = {Philip Hartman}, title = {On oscillators with large frequencies.}, journal = {Bollettino dell'Unione Matematica Italiana}, volume = {14}, year = {1959}, pages = {62-65}, zbl = {0086.07002}, mrnumber = {104859}, language = {en}, url = {http://dml.mathdoc.fr/item/BUMI_1959_3_14_1_62_0} }
Hartman, Philip. On oscillators with large frequencies.. Bollettino dell'Unione Matematica Italiana, Tome 14 (1959) pp. 62-65. http://gdmltest.u-ga.fr/item/BUMI_1959_3_14_1_62_0/
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